Method and apparatus for increasing the intrinsic viscosity of a polycondensate melt

• US 9,908,263 B2
• Filed: 09/12/2013
• Issued: 03/06/2018
• Est. Priority Date: 09/12/2012
• Status: Active Grant

• Current Assignee: Next Generation Recyclingmaschinen GmbH
• Original Assignee: Next Generation Recyclingmaschinen GmbH
• Inventors: Pichler, Thomas, Hehenberger, David, Behoun, Helmut, Pichler, Bernhard
• Primary Examiner(s): Hindenlang, Alison L
• Assistant Examiner(s): Luk, Emmanuel S
• Application Number:
  US14/427,364
• Publication Number:
  US 20150266209A1
• Time in Patent Office: 1,636 Days
• CPC Class Codes: B29B 7/421 with screw and additionally other mixing elements on the same shaft, e.g. paddles, discs, bearings, rotor blades of the Banbury type
• CPC Class Codes: B29B 7/429 Screws B29B7/421 takes precedence
• CPC Class Codes: B29B 7/60 for feeding, e.g. end guides for the incoming material B29B7/7615 takes precedence; feeding predetermined amounts for mixing in general B01F35/714
• CPC Class Codes: B29B 7/66 Recycling the material B29B7/566 takes precedence
• CPC Class Codes: B29B 7/726 Measuring properties of mixture, e.g. temperature or density B29B7/724 takes precedence
• CPC Class Codes: B29B 7/728 Measuring data of the driving system, e.g. torque, speed, power, vibration B29B7/724 takes precedence
• CPC Class Codes: B29B 9/06 in the form of filamentary material, e.g. combined with extrusion
• CPC Class Codes: B29B 9/16 Auxiliary treatment of granules
• CPC Class Codes: B29C 48/03 characterised by the shape of the extruded material at extrusion
• CPC Class Codes: B29C 48/52 with an outer diameter varying along the longitudinal axis, e.g. for obtaining different thread clearance
• CPC Class Codes: B29C 48/53 having a varying channel depth, e.g. varying the diameter of the longitudinal screw trunk
• CPC Class Codes: B29C 48/54 with additional forward-feeding elements
• CPC Class Codes: B29C 48/56 having grooves or cavities other than the thread or the channel
• CPC Class Codes: B29C 48/59 characterised by details of the thread, i.e. the shape of a single thread of the material-feeding screw
• CPC Class Codes: B29C 48/64 Screws with two or more threads
• CPC Class Codes: B29C 48/645 neighbouring threads and channels having identical configurations
• CPC Class Codes: B29K 2067/003 PET, i.e. poylethylene terephthalate
• CPC Class Codes: C08G 63/785 characterised by the apparatus used
• CPC Class Codes: C08G 85/002 Post-polymerisation treatment
• CPC Class Codes: C08J 11/06 without chemical reactions
• CPC Class Codes: C08J 2367/02 : Polyesters derived from dicarboxylic acids and dihydroxy compounds; C08J2367/06 takes precedence
• CPC Class Codes: Y02W 30/62 : Plastics recycling; Rubber recycling

Abstract

In a method and an apparatus for increasing the intrinsic viscosity of a polycondensate melt at negative pressure, the melt enters a chamber, in which a negative pressure of less than 20 mbar prevails, through a perforated plate or a screen having openings with a diameter of less than 0.5 mm. The melt passes through this chamber in free fall in thin threads and remains in a reservoir beneath the chamber for at least one minute. The melt is moved constantly in the reservoir, and discharged from the reservoir, by a helical mixing and discharge part.

Claims

1. A method for increasing the intrinsic viscosity of a polycondensate melt under negative pressure, in which the melt enters a chamber via a connection opening and through a perforated plate or a screen with a plurality of openings with a diameter of less than 0.5 mm, in which chamber there is a pressure of less than 20 mbar, wherein the melt passes through said chamber in free fall in the form of thin threads, and wherein the thin threads are returned to a melt bath and the melt remains in a reservoir below the chamber, wherein the melt remains in the reservoir for at least one minute and the melt in the reservoir is moved continually by a mixing and discharge element under a pressure of less than 20 mbar and the mixing and discharge element is aligned in a horizontal position, wherein a height of the melt bath in the reservoir is selected to be so high that the mixing and discharge element in the reservoir is not completely covered by the melt and thereby the surface of the melt is repeatedly torn up by a rotational movement of the mixing and discharge element and repeatedly renewed, and the polycondensation started with the thin threads is continued in the melt bath by the dwelling period and continuous movement, and thus causes polymer chain growth and thereby increases the intrinsic viscosity further and the melt is discharged from the reservoir laterally by the mixing and discharge element.

2. The method as claimed in claim 1, wherein in the chamber there is a pressure of below 10 mbar.

3. The method as claimed in claim 1, wherein there is a dried gas or an inert gas in the chamber.

4. The method as claimed in claim 1, wherein the melt enters the chamber through openings with a diameter of between 0.05 and 0.5 mm.

5. The method as claimed in claim 1, wherein the dwelling time of the melt in the reservoir is at least 1 to 2 minutes.

6. The method as claimed in claim 5, wherein the dwelling time of the melt in the reservoir is up to twelve, fourteen or sixteen minutes.

7. The method as claimed in claim 1, wherein after the mixing and discharge element an in-line viscosity measurement of the melt is performed and the intrinsic viscosity of the melt is controlled by changing the negative pressure.

8. The method as claimed in claim 1, wherein the melt passes through at least two chambers consecutively.

9. The method as claimed in claim 8, wherein the melt between two chambers is kept at the required melt temperature by a temperature control device.

10. The method as claimed in claim 1, wherein the mixing and discharge element discharges the melt from the reservoir into a collecting line, and

wherein the mixing and discharge element extends into the connecting line.